Change the refs to Line Type and Line Description in line 3 back to @1 and @2. These field names do not exist in the data source, so you can't reference them at this point.
Alternatively, do a two level load like this:
[Line Type] & ' - ' & [Line Description] AS [Transaction Type];
Load @1 AS [Line Type],
@2 AS [Line Description]
From etc etc....
Don't forget the semicolon before the second Load statement.